The use of sensors is well-known in the manufacture and handling of sheet material, for guiding the material through the various stages of a processing plant. For example, sensors may be employed to detect the edges of a web for generating an edge position signal for use in controlling the position of the web in relation to individual work stations. Alternatively, sensors may be employed for detecting the presence of a splice in a web for generating a splice indication output for activating apparatus at a selected work station, eg. for cutting the web.